The present invention relates generally to the art of speed reducers of the type including an output hub for mounting to a shaft to be driven. More particularly, the present invention relates to a mounting arrangement for such a speed reducer which is adaptable to a variety of shaft configurations.
In many applications, it is desirable to utilize a speed reducer which does not itself have an output shaft, but instead mounts to an existing shaft. For example, it will frequently be desirable to mount a speed reducer to a pulley shaft in a belt conveyor system. Typically, the shaft in this case may serve as the primary means by which the speed reducer is supported. An arm member may also be provided to resist torque which would otherwise tend to rotate the speed reducer housing about the output hub.
Various arrangements have been provided to secure the output hub of the speed reducer to the shaft. In a typical arrangement, the output hub includes one or more tapered surfaces on its interior. A sleeve member having a tapered exterior surface is moved into the hub to engage one of the tapered interior surfaces. The sleeve member includes a slot which allows contraction about the shaft when the complementary tapered surfaces are brought into engagement. Examples of such arrangements are shown in U.S. Pat. No. 4,626,114 to Phillips and U.S. Pat. No. 3,590,652 to Strang, each incorporated herein by reference.
Similar speed reducers are often utilized in applications involving a screw conveyor. A screw conveyor typically includes an elongated auger mounted within an appropriate trough. The auger is driven by a shaft secured to the output hub of the speed reducer. In this case, the speed reducer itself typically serves to support one end of the shaft and auger. The other end of the auger is generally supported by an appropriate bearing at the opposite end of the trough. A particulate material, such as grain or sand, is conveyed down the trough by rotation of the auger.
In a screw conveyor, the load imposed on the auger by the conveyed material will sometimes impart a significant axial force to the shaft. Because of the axial force imparted on the shaft, as well as the difficulty in machining a matching taper on the drive shaft, screw conveyor applications have typically not utilized tapered sleeve mounting arrangements such as that described above. Instead, a reduced diameter portion of the shaft is typically mounted in a straight hub such that a face of the hub abuts a shoulder defined on the shaft. A retaining plate is attached to the end of the shaft to abut the opposite face of the hub or a snap ring situated in a groove just inside of the end face of the hub. This arrangement "sandwiches" the hub to resist the axial force imparted on the shaft by the conveyor.
In most other respects, such as the drive train, speed reducers utilized for general applications such as belt conveyors and speed reducers utilized with screw conveyors are substantially similar. However, the different mounting arrangements discussed above have required the installation of different output hubs in the speed reducer, depending on the application.
Further, while prior art tapered sleeve mounting arrangements have been effective at securing the output hub to a shaft, they have not been as versatile as would often be desirable. For example, it would be desirable to provide a speed reducer in which the same hub could be used for applications requiring tapered sleeves as well as applications requiring attachment without tapered sleeves. An arrangement would also be desirable which permitted the optional use of one or two tapered sleeves. In addition, enhanced versatility would be provided by a single tapered sleeve that is mountable from either side of the speed reducer. It would also be desirable to provide an arrangement whereby the speed reducer may be secured to a shaft which does not extend completely through the output hub.